The nineteenth century witnessed the conversions of two prominent Anglican clergymen to Roman Catholicism. Both men would ultimately become cardinals in the Roman Church, and both men would profoundly influence Roman Catholic theology. The first was John Henry Newman (1801–1890). The second was Henry Edward Manning (1808–1892). Newman is probably most well known for his involvement in the high church Oxford Movement and for his Essay on the Development of Christian Doctrine (1845). Manning is best known for his advocacy of social justice and for his strong support of the doctrine of papal infallibility following his conversion to Rome. He...